KR101627830B1 - A non-zero dispersion shifted optical fiber and optical transmission line using the same, and optical transmission system - Google Patents

Abstract

The present invention relates to a single mode optical fiber capable of WDM (wavelength division multiplexing) transmission not only in the SCL band but also in the O-band wavelength band, and is characterized in that the absolute value of dispersion at a wavelength of 1,310 nm is 17.0 ps / nm- And is characterized by having an effective cross-sectional area as large as 1,260 nm or less, and having excellent bending loss characteristics.

Nonlinear dispersion-shifted optical fiber, O-band, cut-off wavelength, bending loss

Description

TECHNICAL FIELD [0001] The present invention relates to an optical fiber capable of transmitting a single mode in a wide band, an optical transmission line using the optical fiber, and an optical communication system using the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber suitable as an optical transmission line used in a WDM (Wavelength Division Multiplexing) transmission system, and is capable of transmitting a single mode over an SCL band (1460 to 1625 nm) and a 0 band (1285 nm to 1330 nm) And a single mode optical fiber having a high effective cross-sectional area with a cut-off wavelength of 1260 nm or less and excellent bending loss characteristics.

In a wavelength division multiplexing (WDM) optical communication network that transmits a large amount of information, optical signals having N different wavelengths are multiplexed and transmitted simultaneously through a single optical fiber. The optical signal transmitted through the optical fiber mainly uses the C-band in the 1530 nm to 1565 nm wavelength band and the L-band in the 1570 nm to 1605 nm wavelength band, which have good transmission characteristics.

As the environment of the WDM transmission system changes, various optical fibers suitable for this have been proposed.

First, in order to suppress nonlinear phenomena such as Four Wave Mixing, a non-zero dispersion-shifted optical fiber having a constant dispersion value at a wavelength of 1,550 nm and a large effective area is classified into ITU- T standard.

standard
MFD @ 1550 nm cable
Cut-off wavelength The zero dispersion wavelength ([lambda] o) [nm] Dispersion value [ps / nm-km] 1530 nm 1550 nm 1565 nm 1625 nm Slope G.655.A 8.0 to 11.0 + - 0.7 1450nm - ≥0.1 - ≤ 6.0 - -

(Slope: dispersion slope [ps / nm ² -km], MFD @ 1550 nm: mode field diameter at 1,550 nm)

In addition, Korean Patent Laid-Open No. 2001-99644 (titled "Positive dispersion, optical fiber with low dispersion slope") (hereinafter abbreviated as "Patent Document 1") is an optical fiber .

Effective area
[탆 ² ] MFD @ 1530 nm ~ 1570 nm cable
Cut-off wavelength Zero dispersion wavelength
([lambda] o) [nm] Dispersion value [ps / nm-km] 1530 nm 1550 nm 1565 nm 1625 nm Slope > 60 8.8 to 10.6 - 1465-1530 ≥ 2.0 - - 13.0 ≪ 0.1

(Slope: dispersion slope [ps / nm ² -km], MFD @ 1550 nm to 1570 nm: mode field diameter at 1,530 nm to 1,570 nm)

In ITU-T, G.656 is proposed as a standard for optical fibers that can be used in all S-band, C-band, and L-band bands for CWDM communication. It is a new standard that the used wavelength band is extended. G.656 has a dispersion value of 1.0 to 14.0 ps / nm-km in the entire band (1460 nm to 1625 nm) of the S-band, C-band and L-band and satisfies the optical characteristics shown in Table 3 below .

standard
MFD @ 1550 nm cable
Cut-off wavelength The zero dispersion wavelength ([lambda] o) [nm] Dispersion value [ps / nm-km] 1460 nm 1550 nm
1625 nm Slope G.656 7.0 to 11.0 + - 0.7 1450nm - 1.00 to 4.60 3.60 to 9.28 4.58 to 14.00 -

(Slope: dispersion slope [ps / nm ² -km], MFD @ 1550 nm: mode field diameter at 1,550 nm)

In addition, Korean Patent Publication No. 2002-59769 (entitled "Dispersion Shift Waveguide Fiber Having a Large Effective Area") (hereinafter abbreviated as "Patent Document 2") proposes an optical fiber having optical characteristics as shown in Table 4 below Respectively.

Effective area
[탆 ² ] MFD @ 1550 nm cable
Cut-off wavelength Zero dispersion wavelength
([lambda] o) [nm] Dispersion value [ps / nm-km] 1470 nm 1550 nm 1565 nm 1625 nm Slope > 60 - - ≤1450 ≥1.0 - - ≤16.0 ≪ 0.1

(Slope: dispersion slope [ps / nm ² -km], MFD @ 1550 nm: mode field diameter at 1,550 nm)

The optical fiber satisfying the standard of G.655.A and the optical fiber of the above Patent Document 1 are not only positioned in the E-band for the purpose of use in the C-band and the L-band, And thus does not satisfy the single mode transmission and dispersion characteristics in the O-band.

In addition, the optical fiber satisfying the standard of G.656 and the optical fiber of Patent Document 2 are characterized not only by the C-band and the L-band, but also by the S-band and the dispersion slope is designed to be small . However, this has the disadvantage that the effective cross-sectional area of the optical fiber is smaller than the above-mentioned G.655.A and the nonlinear characteristic deteriorates.

The present invention provides a single mode optical fiber capable of WDM transmission in a wide wavelength band ranging from 1280 nm to 1700 nm. In particular, it is an object of the present invention to provide a single mode optical fiber having a cutoff wavelength of 1260 nm or less, a high effective cross-sectional area, and excellent bending loss characteristics.

The present invention also provides an optical transmission line using the optical fiber and an optical communication system employing the optical transmission line.

Other objects and advantages of the present invention will be described hereinafter and will be understood by the embodiments of the present invention. Further, objects and advantages of the present invention can be realized by the means and the combination shown in the appended claims.

A single mode optical fiber for Wavelength Division Multiplexing Transmission in the wavelength band of 1,300 to 1,700 nm according to the first aspect of the present invention is characterized in that (a) an absolute value of dispersion at a wavelength of 1,310 nm is 17.0 ps / nm-km or less and, a zero-dispersion wavelength of 1,500nm or less, dispersion slope of 0.08ps / nm ² -km or less, (b) and the cut-off wavelength is 1,260nm or less, the effective area is 65 ~ 80㎛ ^2, (c) diameter of 32mm , And the bending loss at a wavelength of 1,625 nm is 0.5 dB or less under 1 turn condition.

The optical fiber of the first aspect has a dispersion value at a wavelength of 1,530 nm of 2.0 ps / nm-km or more, a dispersion value at a wavelength of 1,565 nm of 6.0 ps / nm-km or less, Is 11 ps / nm-km or less, and the mode field diameter at a wavelength of 1,550 nm is 9.1 to 10.0 m.

A single mode optical fiber for Wavelength Division Multiplexing Transmission in a wavelength band of 1300 to 1700 nm according to a second aspect of the present invention is characterized in that (1) a single mode optical fiber located at the optical center axis and having a radius r ₁ from the optical center axis, relative refractive index difference surround the △ ₁ in the first core region and the first core region, the radius from the optically central axis and r _2, and the specific refractive index difference surround the △ ₂ of the second core region and second core region a and having a radius from the optical center axis r _3, and the specific refractive index difference △ ₃ of the third core region, and the third surrounding the core region, the radius from the optical center axis r _4, and the relative refractive index difference △ ₄ second A multi-core layer composed of four core regions; A clad layer surrounding the multi-core layer; (2) The refractive index profile in which the radius of each of the regions is r ₁ <r ₂ <r ₃ <r ₄ and the difference in refractive index is Δ ₁ > Δ ₃ > Δ ₂ ≥Δ ₄ and Δ ₂ , Δ _4, with, _{(where, △ 1 (%) = [} (n 1 -n c) / n c] × 100, △ 2 (%) = [(n 2 -n c) / n c] × 100, △ 3 ( _{%) = [(n 3 -n} c) / n c] × 100, △ 4 (%) = [(n 4 -n c) / n c] × 100, n 1: refractive index of the first core region, n _2: a second core region has a refractive index of, n _3: the third core region of refractive index, _{n. 4:} refractive index of the fourth core region, n _c: refractive index of the cladding layer), (3) the absolute value of dispersion at 1310nm wavelength 17ps / nm-km and the cut-off wavelength is 1,260 nm or less. The first core region preferably has a trapezoidal refractive index distribution, more preferably an effective cross-sectional area of 65 to 80 탆 ² , and a bending loss at a wavelength of 1,625 nm of 0.5 dB or less under a 1 turn condition of a diameter of 32 mm.

The optical fiber according to the second aspect of the present invention has a zero dispersion wavelength of 1,500 nm or less, a dispersion slope of 0.08 ps / nm ² -km or less, a dispersion value at a wavelength of 1,530 nm of 2.0 ps / nm- , A dispersion value at a wavelength of 1,565 nm is 6.0 ps / nm-km or less, and a dispersion value at a wavelength of 1,625 nm is 11 ps / nm-km or less.

It is also preferable that the mode field diameter at a wavelength of 1,550 nm is 9.1 to 10.0 mu m.

The optical fiber of the present invention enables single-mode optical transmission based on wavelength division multiplexing (WDM) in a wide wavelength band ranging from O-band (1260 nm to 1360 nm) to L-band (1565 nm to 1625 nm).

Conventional G.655.A standard optical fibers (see Table 1) and G.656 standard optical fibers (see Table 3) have the disadvantage that the optical transmission wavelength band is limited to the C-L band or the S-C-L band. Accordingly, the present invention extends the optical transmission wavelength band to O-band (1,260 nm to 1,360 nm) by limiting the cutoff wavelength to 1,260 nm or less and limiting the dispersion value at 1,310 nm to 17.0 ps / nm-km or less have. To this end, the present invention is characterized in that the effective cross-sectional area is maintained at the same level as that of the conventional G.655.A standard optical fiber or G.656 standard optical fiber even when the cut-off wavelength is reduced to 1,260 nm. However, when the effective cross-sectional area is the same, there arises a problem that the bending loss characteristic increases as the cut-off wavelength decreases.

In order to solve such a problem, the present invention proposes a single mode optical fiber having a refractive index profile as shown in Figs.

1 and 2, the optical fiber according to the present invention includes a first core region 1a having a radius r ₁ from the optical center axis and a difference in refractive index of Δ ₁ ; The first surrounds the core region and having a radius from the optical center axis r _2, and the specific refractive index difference △ ₂ of the second core region (1b) and; A third core region (1c) surrounding the second core region, the third core region (1c) having a radius r ₃ from the optical center axis and a difference in refractive index of? ₃ ; And a fourth core region (1d) surrounding the third core region, the fourth core region (1d) having a radius r ₄ from the optical center axis and a non-refractive index difference of? ₄ , and a cladding layer Layer (2). Also, the first core region (1a) has a trapezoidal refractive index profile having a top portion with a radius r ₁ '.

That is, the optical fiber of the present invention has a refractive index profile with a radius r ₁ <r ₂ <r ₃ <r ₄ and a difference in refractive index Δ ₁ > Δ ₃ > Δ ₂ ≥Δ ₄ and Δ ₂ , Δ _4, .

_{Here, △ 1 (%) = [} (n 1 -n c) / n c] × 100, △ 2 (%) = [(n 2 -n c) / n c] × 100, △ 3 (%) = _{[(n 3 -n c) /} n c] × 100, △ 4 (%) = [(n 4 -n c) / n c] × 100, n 1: refractive index of the first core region, n _2: the N ₃ is the refractive index of the third core region, n ₄ is the refractive index of the fourth core region, and n _c is the refractive index of the clad layer.

Further, in the present invention, POCl ₃ in the fourth core region 1d is removed to maintain the effective cross-sectional area at 65 to 80 탆 ² and to improve the bending loss characteristic while lowering the cut-off wavelength to 1,260 nm or less. By thus removing POCl ₃ at the time of manufacturing the fourth core region, it is possible to reduce the change of the non-refractive index difference? ₄ according to the change of the tensile strength by increasing the viscosity. As a result, it is possible to obtain a constant bending loss characteristic (bending loss at a wavelength of 1,625 nm: 0.5 dB or less at a diameter of 32 mm and 1 turn condition) by designing a small Δ ₄ after pulling.

The optical characteristics of the optical fiber according to the present invention having the refractive index profile of FIG. 1 are as follows.

(1) Effective sectional area [占 퐉 ² ]: 65 to 80 占 퐉 ² [1550 nm]

(2) Mode field diameter at 1,550 nm (MFD @ 1,550 nm) [占 퐉]: 9.1 to 10.0 占 퐉

(3) Breaking wavelength [nm]: 1,260 nm or less

(4) Young's dispersion wavelength (? _O ) [nm]: 1,500 nm or less

(5) dispersion value [ps / nm-km]

1,310 nm: -17.0 ps / nm-km or more

1.530 nm: 2.0 ps / nm-km or more

1.565 nm: 6.0 ps / nm-km or less

1.625 nm: 11 ps / nm-km or less

6, dispersion slope ^{[ps / nm 2 -km]:} 0.08ps / nm 2 -km or less

(7) Bending loss [dB]

Bending loss at 1,625nm wavelength at a diameter of 32mm, 1 turn condition: less than 0.5dB

<Manufacturing Method of Optical Fiber>

A quartz tube having a refractive index profile as shown in Fig. 1 and having an optical characteristic as described above is prepared by the MCVD method. The fourth core layer 1d is formed by depositing soot particles by heating the outer circumferential surface of the quartz tube while introducing a raw material gas composed of SiCl ₄ and GeCl ₄ into the thus prepared quartz tube together with oxygen and sintering. At this time, since the POCl ₃ is removed from the raw material gas, it is possible to reduce the change in the specific refractive index difference? ₄ according to the change in the tensile strength by increasing the viscosity of the vapor deposition layer. As a result, it is possible to obtain a constant bending loss characteristic (bending loss at a wavelength of 1,625 nm: 0.5 dB or less at a diameter of 32 mm and 1 turn condition) by designing a small Δ ₄ after pulling.

On the other hand, the soot particles are deposited and sintered by heating the outer circumferential surface of the quartz tube while introducing a raw material gas composed of SiCl ₄ , GeCl ₄ and POCl ₃ into the quartz tube formed with the fourth core layer together with oxygen, To third core layers (1a, 1b, 1c)) are formed. At this time, since POCl ₃ is added to the raw material gas, it is possible to lower the production temperature for producing the optical fiber preform.

When the hollow base material in which the first to fourth core layers 1a to 1d are formed in the quartz tube is completed, a parent material is produced through a condensation process. This mother tailing is completed with an optical fiber according to the present invention through a known RIT process and a wire drawing process.

Another aspect of the present invention relates to an optical transmission line using the optical fiber and an optical communication system employing the optical transmission line as at least a part of an optical transmission path.

Example 1

1 and has a radius of r ₁ = 2.8 ± 0.6 μm, r ₂ = 4.3 ± 0.6 μm, r ₃ = 5.5 ± 0.6 μm, and r ₄ = 6.5 ± 0.6 μm , and the relative refractive index difference between each of _{△ 1 (%) = 0.51 ±} 0.03%, △ 2 (%) = -0.14 ± 0.03%, △ 3 (%) = 0.25 0.03%,? ₄ (%) = -0.15 + 0.03%. The thus fabricated optical fiber has the following optical characteristics.

(1) Young's dispersion wavelength: 1,486 nm

(2) The variance value

1.310 nm: -15.2 ps / nm-km, 1.530 nm: 3.25 ps / nm-km,

1.565 nm: 5.8 ps / nm-km, 1,625 nm: 10.63 ps / nm-km

(3) dispersion slope ^{[ps / nm 2 -km]:} 0.073ps / nm 2 -km

(4) Effective sectional area: 72 탆 ² [1,550 nm]

(5) Cut-off wavelength: 1,119 nm

(6) Mode field diameter (MFD) (1,550 nm): 9.56 탆

(7) bending loss at 1,625 nm wavelength at a diameter of 32 mm, 1 turn condition: 0.15 dB

Example 2

1 and has a radius of r ₁ = 2.8 ± 0.6 μm, r ₂ = 4.3 ± 0.6 μm, r ₃ = 5.5 ± 0.6 μm, and r ₄ = 6.5 ± 0.6 μm , and the relative refractive index difference between each of _{△ 1 (%) = 0.51 ±} 0.03%, △ 2 (%) = -0.14 ± 0.03%, △ 3 (%) = 0.25 0.03%,? ₄ (%) = -0.15 + 0.03%. The thus fabricated optical fiber has the following optical characteristics.

(1) Young's dispersion wavelength: 1,494 nm

(2) The variance value

1.310 nm: -16.1 ps / nm-km, 1.530 nm: 2.62 ps / nm-km,

1.565 nm: 5.12 ps / nm-km, 1,625 nm: 9.5 ps / nm-km

(3) dispersion slope ^{[ps / nm 2 -km]:} 0.073ps / nm 2 -km

(4) Effective sectional area: 69 탆 ² [1,550 nm]

(5) Cut-off wavelength: 1,154 nm

(6) Mode field diameter (MFD) (1,550 nm): 9.37 탆

(7) bending loss at a wavelength of 1,625 nm at a diameter of 32 mm, 1 turn condition: 0.13 dB

Example 3

1 and has a radius of r ₁ = 2.8 ± 0.6 μm, r ₂ = 4.3 ± 0.6 μm, r ₃ = 5.5 ± 0.6 μm, and r ₄ = 6.5 ± 0.6 μm , and the relative refractive index difference between each of _{△ 1 (%) = 0.51 ±} 0.03%, △ 2 (%) = -0.14 ± 0.03%, △ 3 (%) = 0.25 0.03%,? ₄ (%) = -0.15 + 0.03%. The thus fabricated optical fiber has the following optical characteristics.

(1) Zero dispersion wavelength: 1,482 nm

(2) The variance value

1.310 nm: -15.5 ps / nm-km, 1.530 nm: 3.49 ps / nm-km,

1.565 nm: 5.96 ps / nm-km, 1,625 nm: 10.48 ps / nm-km

(3) dispersion slope ^{[ps / nm 2 -km]:} 0.074ps / nm 2 -km

(4) Effective sectional area: 75 탆 ² [1,550 nm]

(5) Cutoff wavelength: 1,076 nm

(6) Mode field diameter (MFD) (1,550 nm): 9.75 탆

(7) bending loss at a wavelength of 1,625 nm at a diameter of 32 mm, 1 turn condition: 0.17 dB

The optical fibers of Examples 1 to 3 all had a cut-off wavelength of 1,260 nm or less, an absolute dispersion value at 1,310 nm of 17.0 ps / nm-km or less, a diameter of 32 mm, a wavelength of 1,625 nm The bending loss in the case of the first embodiment satisfies 0.5 dB or less. Therefore, it can be confirmed that single mode optical transmission is possible in the O-band as well as in the S-C-L band.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the detailed description of the invention given below, serve to further the understanding of the technical idea of the invention, Should not be construed as limiting

1 is a structural view of a refractive index profile of an optical fiber according to the present invention.

2 is a cross-sectional view of a multi-core layer and a cladding layer of an optical fiber according to the present invention.

Claims (11)

Mode optical fiber for Wavelength Division Multiplexing Transmission in a wavelength band of 1,300 to 1,700 nm, The optical fiber (a) an absolute value of dispersion at a wavelength of 1,310 nm is 17.0 ps / nm-km or less, a zero dispersion wavelength is 1,500 nm or less, a dispersion slope is 0.08 ps / nm ² -km or less, (b) the cut-off wavelength is 1,260 nm or less, the effective cross-sectional area is 65 to 80 탆 ² , (c) a bending loss at a wavelength of 1,625 nm is 0.5 dB or less at a diameter of 32 mm and a 1 turn condition. The method according to claim 1, A dispersion value at a wavelength of 1,530 nm is 2.0 ps / nm-km or more, a dispersion value at a wavelength of 1,565 nm is 6.0 ps / nm-km or less, and a dispersion value at a wavelength of 1,625 nm is 11 ps / Features a fiber optic. 3. The method according to claim 1 or 2, Wherein the mode field diameter at a wavelength of 1,550 nm is 9.1 to 10.0 占 퐉. Mode optical fiber for Wavelength Division Multiplexing Transmission in a wavelength band of 1300 to 1700 nm, The optical fiber (1) a first core region located at the optical center axis and having a radius r ₁ from the optical center axis and a difference in refractive index of Δ ₁ , and a second core region surrounding the first core region and having a radius r ₂ from the optical center axis , relative refractive index difference surround the △ ₂ of the second core region and second core region and having a radius from the optical center axis r _3, a relative refractive index difference △ ₃ of the third core region, and the third core region A multi-core layer surrounding the fourth core region, the fourth core region having a radius r ₄ from the optical center axis and a non-refractive index difference of? ₄ ; A clad layer surrounding the multi-core layer; (2) The refractive index profile in which the radius of each of the regions is r ₁ <r ₂ <r ₃ <r ₄ and the difference in refractive index is Δ ₁ > Δ ₃ > Δ ₂ ≥Δ ₄ and Δ ₂ , Δ _4, have, _{(Where, △ 1 (%) = [} (n 1 -n c) / n c] × 100, △ 2 (%) = [(n 2 -n c) / n c] × 100, △ 3 (%) _{= [(n 3 -n c)} / n c] × 100, △ 4 (%) = [(n 4 -n c) / n c] × 100, n 1: refractive index of the first core region, n _2: a second core region of refractive index, n _3: refractive index of the third core region, n _4: refractive index of the core region 4, n _c: refractive index of the cladding layer) (3) the absolute value of dispersion at 1310 nm wavelength is 17 ps / nm-km or less, the cutoff wavelength is 1,260 nm or less, (4) An optical fiber having an effective cross-sectional area of 65 to 80 탆 ² and a bending loss at a wavelength of 1,625 nm of 0.5 dB or less under a 1 turn condition of a diameter of 32 mm. 5. The method of claim 4, Wherein the first core region has a trapezoidal refractive index profile. delete The method according to claim 4 or 5, Wherein the zero dispersion wavelength is 1,500 nm or less and the dispersion slope is 0.08 ps / nm &lt; ² &gt; -km or less. 8. The method of claim 7, A dispersion value at a wavelength of 1,530 nm is 2.0 ps / nm-km or more, a dispersion value at a wavelength of 1,565 nm is 6.0 ps / nm-km or less, and a dispersion value at a wavelength of 1,625 nm is 11 ps / Features a fiber optic. 9. The method of claim 8, Wherein the mode field diameter at a wavelength of 1,550 nm is 9.1 to 10.0 占 퐉. An optical transmission line employing the single mode optical fiber according to any one of claims 1 to 4. The optical communication system according to claim 10, wherein the optical transmission line is employed as at least a part of an optical transmission path.

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